The invention relates to a brake actuator, particularly for a rail vehicle caliper for a disk brake
From German Patent Document DE 195 14 463 C1, a caliper unit for disk brakes of vehicles, particularly rail vehicles, is known which has a caliper with two caliper levers, one of these caliper levers being operable by way of an eccentric transmission and the other caliper being disposed on a housing. This caliper unit represents a brake actuator which, on the one hand, has an electric-motor drive and, on the other hand, comprises a safety braking unit with an accumulator device for the application of the brake.
German Patent Document DE 198 04 454 A1 shows an electromechanically operable disk brake for motor vehicles. In the case of this disk brake, the reduction gear is constructed as a roller thread gear with a return of the thread rollers.
German Patent Document DE 30 48 766 shows an application device for parking brakes of rail vehicles, which is also operated by an electric motor. By way of a reduction gear, this electric motor has a conversion gear for converting the rotating movement to a longitudinal movement of an actuating member.
Furthermore, European Patent Document EP 0 129 969 shows a brake actuator which permits by way of an electric motor arrangement the tensioning of a spring generating a braking force.
Essentially, two wheel brake systems are currently used in the rail vehicle field: Pneumatic braking systems (which also may include electropneumatic systems and vacuum brakes) and (electro)hydraulic braking systems. So far, purely electromechanical braking systems have not been significantly successful on the market.
In both technologies, the generating of force is implemented by pistons in cylinders which generally have only one operative direction. The restoring of the pistons takes place as a result of the forces, which occur because of the elastic deformation of the brake linkage, as well as as a result of restoring springs which, in addition, ensure the taking-up of an end position.
The local energy accumulation for the possibility of supply interruptions, in the case of pneumatic systems, takes place in compressed-air reservoirs, or, in the case of hydraulic systems in corresponding hydraulic reservoirs and, in the case of electromechanical systems, by booster batteries or a redundant power supply. In addition, passive systems contain the possibility of a one-time application by the energy accumulated in the spring.
Based on this background, it is an object of the invention to provide a brake actuator which ensures a high operational reliability and has a compact and cost-effective construction.
The invention achieves this goal by means of the object of Claim 1. In contrast to the prior art, the pre-loaded spring device and the brake spindle are arranged coaxially with respect to one another, which indicates a very space-saving and cost-effective arrangement of these structural members. As a result of this arrangement, it is also possible to connect the brake spindle and the pre-loaded spring mechanically xe2x80x9cin seriesxe2x80x9d in a simple manner such that it is prevented that, in the case of a service brake, they jointly generate the braking force. The safety spring can be utilized as a parking brake and also as an emergency brake in the case of a defect (such as a power failure, a failure of the electronic system or a motor failure). The low energy requirement while the braking forces are low is also an advantage.
Additional advantageous embodiments of the invention are contained in the remaining subclaims.